</fileset>
                </copy>
              </target>
            </configuration>
          </execution>
        </executions>
      </plugin>
      <!-- TODO(cpovirk): We really should try tbroyer's plugin instead of this legacy one. -->
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>gwt-maven-plugin</artifactId>

              <arg>-XDcompilePolicy=simple</arg>
              <arg>--should-stop=ifError=FLOW</arg>

              <!-- https://errorprone.info/docs/installation#maven -->
              <!-- TODO(cpovirk): Enable NullArgumentForNonNullParameter for
                   prod code. It's disabled automatically for "test code"
                   (which is good: our tests have intentional violations), but

              <arg>-XDcompilePolicy=simple</arg>
              <arg>--should-stop=ifError=FLOW</arg>

              <!-- https://errorprone.info/docs/installation#maven -->
              <!-- TODO(cpovirk): Enable NullArgumentForNonNullParameter for
                   prod code. It's disabled automatically for "test code"
                   (which is good: our tests have intentional violations), but

   * bufferSize ≥ k, then we can ignore any elements greater than this value.
   */
  private @Nullable T threshold;

  @SuppressWarnings("unchecked") // TODO(cpovirk): Consider storing Object[] instead of T[].
  private TopKSelector(Comparator<? super T> comparator, int k) {
    this.comparator = checkNotNull(comparator, "comparator");
    this.k = k;